Description of Prior Art
For many years significant efforts have been made to develop systems that reliably establish the identity of a person. More recently, systems have attempted to link that identity verification to the verification of the date and to the verification and authentication of the content of a message generated or transmitted electronically. Such systems are deemed desirable from the point of view of both the identifier and the identified in a variety of settings. Some uses for identify verification systems include: credit card transactions, access to computer programs and information, electronic funds transfer, and the electronic transmission of legal documents and signatures. In these types of situations identity verification must be inexpensive, reliable, and non-intrusive.
Many proposed systems measure some biological trait unique to the individual. Reference measurements are taken and stored for comparison later at the time of verification. For example, there exist systems using voice recognition, palm print recognition, and laser retinal scans. These systems have achieved some success in terms of reliability and utility in restricted situations. Retinal scanners are used in some prisons and high security areas in government and industry. However, the public perception of intrusiveness has kept such systems from widespread applications in everyday transactions. Complexity of the systems and costs have also slowed development and implementation.
Identity verification by means of written signatures, electronically recorded, has long been known, in spite of significant shortcomings. One advantage of systems using the familiar signature and pen is that intrusiveness is not considered a problem. The signature is commonplace and expected in everyday financial transactions and as a means of general identification. Also, a major advantage of signatures as identification is the unique role that the signature plays in human affairs. The signature of ink on paper has been, and continues to be, the quintessential mark of business. No substitute for the signature is likely to be developed. Contracts, credit card slips, and checks become legal, once signed. The requirement of legal signatures on documents increasingly causes a bottleneck when the rest of the information and documentation is transmitted electronically.
Dynamic signature verification typically records the various pressures, velocities, accelerations, and directions of writing by means of transducers or accelerometers housed in a special pen or writing plenum. Reference signatures are acquired during an enrollment process. The electronic signals from the reference signatures are analyzed and stored for comparison to offered signatures during a verification transaction.
Dynamic signature verification systems should be distinguished from systems designed just to capture a signature and replicate it later without verification. Also, plenum (or pad-based) systems which house electronic devices in the writing pad rather than the pen itself should be distinguished. The system described herein consists of a stylus (pen) containing pressure sensing transducers, a unit for amplifying, digitizing, sampling, storing, and transmitting these signals via phone. Finally, algorithms are developed for the analysis of the specific and unique type of signals sent by the data input stylus. Special algorithms are developed for the processing of signal trains from signatures for enrollment of reference signatures and for enrollment of the digits 0-9, and for later verification of identity of persons, date, and content of electronic messages.
Digitized signatures alone do not solve all of the problems relating to authenticity of documents transmitted or preserved in an electronic media.
Traditionally, documents preserved on paper and deemed to be important are printed or typed with no room for additions later, signed in ink by those involved, and the date is written after the signature in ink. In addition, the document might be witnessed and signed by another party and/or stamped with a dated seal of a notary. These are the routine safeguards in place at present for important documents preserved on paper.
The digitization of data, while presenting new opportunities for rapid transmission and easy storage, also presents some new problems. Even if accompanied by a digitized signature, the integrity of the electronic transmission of a signed document may not be preserved to the level of the paper standard of protection. For example, at least for electronic transmission of a signed document, three possibilities for deception exist:
1. The digitized signature might be recorded and played back in lieu of the pen generated signature for forgery purposes. PA1 2. The text of the electronic document might be modified above the signature without apparent tempering. PA1 3. The date of an electronic document could be changed at will, electronically. These types of problems have been dealt with extensively by researchers at Stanford University and MIT using a 2 key cryptosystem--individuals having a "private key" and "public key" to insure the integrity of electronic messages. The National Institute of Standards and Technology is also working along similar lines to develop a digital-signature standard based on the public-key system. Key encryption systems, however, attempt to produce a non-biometric "digital signature" which is fundamentally different from the digitized biometric electronic signature described herein.